This invention relates to angioplasty catheters, and more particularly to percutaneous transluminal laser angioplasty catheters.
The treatment of occlusions, in arteries and blood vessels in general, using an angioplasty catheter equipped with an inflatable balloon at its distal tip, is well known. A more recent technique involves providing an optical fiber in such a catheter, and extending the distal end of the fiber slightly beyond the distal tip of the catheter, whereby laser energy generated at the proximal end of the fiber is transmitted to an occlusion to be treated. For a further explanation of this technique, reference is made to U.S. Pat. No. 4,669,465 and U.S. patent application Ser. No. 887,196 filed July 12, 1986, both assigned to the assignee of this application. An important requirement in using this technique is the proper positioning and orientation of the catheter distal tip. Precise positioning is essential to ensure that laser energy from the optical fiber is directed away from the arterial wall. Improper aiming can result in wall damage or even rupture to the artery.
Apparatus for positioning a catheter distal tip is known, although no necessarily in connection with transmission of laser energy in the catheter. For example, U.S. Pat. No. 4,545,390 to Leary granted Oct. 8, 1985 shows a guide wire with a helical spring attached to a tapered distal end. An extension of the spring is flexible and can be bent into a curve, whereupon insertion can be guided by rotation of the guide wire at the proximal end. U.S. Pat. No. 4,033,331 to Guss et al granted July 5, 1977 shows a catheter having a bend at its distal end, and a contour wire which can be inserted varying amounts to gradually straighten the bend. Somewhat related subject matter is disclosed in U.S. Pat. No. 4,150,676 to Jackson granted April 24, 1979. An endotracheal tube disclosed by Jackson has an inflatable balloon cuff at its distal end. A filament in a lumen runs the length of the tube, and can be pulled to increase the curvature at the distal end. While each of the devices disclosed in these patents is perhaps suitable for its particular environment, the patents fail to adequately address the need for the precise catheter tip positioning required in laser enhanced angioplasty catheters.
Therefore, it is an object of the present invention to provide a means for accurately establishing the position and orientation of the distal tip of a laser angioplasty catheter when it is inserted int an artery or other vessel.
Another object of the invention is to provide a balloon near the tip of an angioplasty catheter, which balloon is particularly well adapted for centering the catheter distal tip within an artery.
Yet another object of the invention is to provide a catheter balloon adapted for orienting the distal tip of the catheter in response to balloon dilation.